PIN BURN-UP OPTIMIZATION at Dukovany NPP

Abstract

Pin burn-up optimization by FA?s rotations has been used at Dukovany NPP since 1990s.
This method helps us to uniform pin burn-up distribution and can be very important in the
future with upcoming new fuel designs. The main purpose of this paper is to familiarize
reader with benefits of this kind of optimization. Attention was especially paid to some new
rotation evaluation technique explanation and to show the influence of assembly rotation to
maximal pin burn-up.
1. Introduction
Present day tendency of prolonging of fuel cycles and power increase is connected with
higher pin burn-up in the spent fuel assemblies. Fuel assembly rotation is crucial tool for pin
burn-up optimization.
Under the term ?Assembly rotation? we understand rotation of the assembly by 60, 120, 180,
240 or 300 degrees. Fuel assemblies in VVER-440 core cannot be physically rotated because
of fixation peg and loading machine limitation. We can take advantage of the reactor core
symmetry and rotations can be realized by moving fuel assembly to another sixth of the core
as shown on fig. 1.

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